Process of making sulfuric acid.



RI 0.8163918. PATENTED APR. 3, 1906. R. KNIETSGH.

PROCESS OF MAKING SULPURIG ACID.

APPLIOATION FILED JULY 16 1901.

llllllil llllllll E I i i w Q luuull INVENTOR UNITED STATE S PATENT OFFICE.

RUDOLF KNIETSOH, oE LUDWIGSHAFEN-ON-THE-RHINE, GERMANY, ,ASSIGNOR, BY MESNE ASSIGNMENTS, TO GENERAL CHEMICAL COMPANY, A CORPORATION OF NEW YORK.

PROCESS OF MAKING SULFURIC ACID.

Specification of Letters Patent.

Application filed July 16, 1901. Serial No. 68,498.

'To all whom it may concern:

Be it known that I, RUDOLF KNIETSCH, doc tor of philosophy and chemist, a subject of the Kine of Prussia, German Emperor, residing at Timlwigshafen-omthe-Rhine, in the Kingdom of Bavaria, Germany, have invented new and useful Improvements in the Manufacture of Sulfuric Acid, of which the following is a specification.

n the accompanying drawing I have shown an elevation of an absorber in section and of parts adjacent thereto adapted for carrying out my invention. I i

The method hitherto employed for absorbing sulfuric nnhydrid (S0,) manufactured on a commercial scale consists in passing the gas containing the sulfuric anhydrid through absorbers in communication with one another and containing sulfuric acid of various strengths. The concentration of the acid in the vessel nearest the source of the sulfuric anhydrid is greatest, while those farther removed contain weaker and weaker acids. The vessels are arranged in any convenient mannerfor instance, one above the other in the form of terraces or steps-and weak acidsay chamber-acid or acid containing seventyv eight per cent. of H,SO,is allowed to flow into the uppermost vessel, while the gases containing SO first enter the lowest vessel. The acid becomes graduallyenriched in its down- Ward passage, so that in the lowest vessel acid of high concentration, or even fuming sul furic acid, is formed, and this isallowed to flow into receivers. The said process has, however, many defects. The plant is expensive to lay down and work, owing to the lar e number of single apparatus needed and t e careful attendance which is thereby necessitated. Again, the absorbing ap aratus are built of iron, which is practically the only material possible for this purpose-that is, when working on the large scale. It is consequently almost impossible. to' obtain the. manner described elear sulfuric acid technically free from iron, on account of the lat e surface of iron exposed to the action of Sn uric acid of such varying and different concentration. This want of constancy in strength of the acid also makes it exceedingly difficult, if not impossible, in practice to completely condense the sulfuric anh drid, so that not only is sulfuric acid liabie to be lost, but also to escape as an injurious mist into the atmosphere.

' The object of mypresent invention isto remedy the .said defects by providing a method for completely absorbing sulfuric anhydrid by means of a considerably smaller P ant than has hitherto been necessary and at the same time producing a highly-concentrated acid which for technical purposes may be considered free from iron.

I have discovered that sulfuric acid of a stren th varying within narrowlimitsname y, between ninety seven and ninetynine per cent-and preferably containing ninety-ei ht and one-third per cent. of H SO is capab e of absorbing sulfuric anhydrid almost instantaneously and so efficiently that,

if desired, the absorption can be carried out in a single absorbing apparatus. Acids of weaker concentration than ninety-seven per cent. absorb sulfuric anhydrid but slowly and incompletely,for in this case hydratefumes areformed which are then taken up by the acid with great difficulty, even when a long series of absorption vessels is employed. On the other hand, acid containing more than ninet -nine per cent. of H,SO (although no free g sulfuric anhydrid to escape. Another advantage offered by the employment of acid of ninety-seventoninety-nine er cent. forabsorption pur oses is to be ound in the purity of the su furic acid that can therebybe obtained. I have mentioned above that the process hitherto in use for absorbin sulfuric anhydrid gives rise toan acid whic usually contains iron com ounds. I have also mentioned in the speclfication of application for Letters Patent Serial No. 68,499, of even date herewith, that iron is practically insoluble in fuming sulfuric acid containing twenty-seven per cent. or more of free S0,.

I have now further discovered that there is a second de ree of concentration of sulfuric acid, at which the acid has but an exceedin l slight action on iron a paratus, and-that t 11s degree is approximate y the same as that at which the owerof the acid for absorbing sulfuric anhy rid is at its greatest. It is thus possible in one operation to effect a complete ab- 0 is present therein) aflows fumes of sorption of sulfuric anhydrid and to produce a highly-concentrated acid technically free from iron.

sorption apparatus.

nically free from iron, with the aid of-a considerably-smaller plant than has hitherto been possible and without loss of sulfuric acid.

The process of manufacturing sulfuric acid which in view of the aforementioned discovcries l have worked out consists in bringing j sulfuric acid eontaining from ninety-seven to ninety-nine per cent. of 11,50 into an ab- The gaseous sulfuric,

anhydrid or gas containiin the sulfuric anhydrid is then passed throug ithe same and the 1 acid kept to the said degree of concentration i by the uninterrupted introduction of a suitl able quantitv of steam, water, or pure dilute sulfuric acid. moved by suitable means, so that a constant level in the absorption apparatus is maintained.

The following example will serve to further illustrate the nature of my invention and the manner in which the same may best be carried into practical effect: but the invention is not confined to this example.

to ninety-nine per cent. of H to a convenient depth. Fit the vessel with a tube (of material unacted on by sulfuric acid) whose mouth dips into the middle of the absorption liquid and which serves for the introduction of thesteam or diluting liquid. The inflow of thelatter is regulated by a The acid as formed can be re- The absorber shown in the accompanying drawing may be described as follows: 1 is a cast-iron inclosure from the to of which is suspended a cast-iron hood 2, tfie lower edge of which is serrated. The sulfuric-anhydridsupply pipe-3 is connected with the top of the hood. The exit-pipe 4 leads from the to of the inclosure 1. The inclosure 1 is supp ied with sulfuric acid through the stand- )ipe 5, extending to near the bottom of the inc losure, the level of the sulfuric acid within. the molesure 1 being kept above the teeth of the hood. 6 is a faucet through which the finish'edprodnet is drawn off. 7 is a water-tank'in which the inclosure 1 is immersed for cooling and through which a current of water is passed from the pipe 8 to the pipe 9. 10 and 11 are pressure-gages connected, respectively, with the inlet-pipe 3 and the outlet-pipe 4. The outlet-pipe 4 should be wholly or partially of Example: Fill a vessel. preferably of cast- 1 iron and made on the principle of a wash-bot- 1 t le, with sulfuric acid containing ninety-seven valve or by other suitable means. Cause the gases containing the sulfuric anhydrid to pass either by suction or pressure through the absorption liquid. At the same time continuously introduce sufficient steam, water, or

pure dilute sulfuric acid, so that the absorbing acid constantly contains ninety-seven to ninety-nine percent. of ll SO The amount of diluent to be employed is determined and controlled by the examination of the acid produced which is allowed to runoff through an inverted siphon. 001 the absorbing vessel to remove the heat of absorption in any suitable manner.

Instead of directly absorbing the sulfuric anhydrid it can be first mixed with the calculated quantity of steam to form an acid containing ninety-seven to ninety-nine per cent.'of 11,80 the procedure being-otherwise as above described,and the absorption appa- 'ratus can be of any suitable form and is not limited to that of a wash-bottle.

The process hereinbefore described can also be used in combination with that set forth in the specification of the aforesaid application for Letters Patent, Serial No. 68,499, of even date herewith, thus making it possible in one operation to obtain fuming sulfuric acid and lnghly-concentrated sulfuric acid, as well as highly-concentrated acid alone, both techlarger diameter, as at 12, so that-the unabsorbed gas passing away from the receptacle 1 will have a chance to deposit anv hquid that Q it may contain, which will run back into the receptacle 1. 13 is a thermometer for determiningthe temperature in 1. In the operation of the apparatus the attendantcharges the inclosure 1 with sulfuric acid of about the strength of the finished product, using acid of a lower strength or other diluent to replenish the inclosure 1 through the pipe 5.

Now what 1 claim is 1. The improvement in the proce'ssof manufacturing sulfuric acid by the absorption of sulfuric anhydrid in sulfuric acid winch consists in maintaining throughout the o eration the strength of said absorbing acid etwcen ninety-seven and ninety-nine per cent. of

2. The rocess of manufacturing sulfuric 'teredi -23. The herein-described process for manufacturing sulfuric acid, which consists in providing a body of liquid acid of substantially the same strength as the product it is desired to obtain, causing sulfuric anhydrid to be absorbed by said acid and su plyin simultaneously with the sulfuric an ydric? a sufficient amount of a diluting agent to said body of liq- I uid acid, to keep said liquid acid at a constant degree of concentration from the beginning of the operation to the end.

'IOO

. 4. The liirocess of manufacturing sulfuric In testimony whereof I llfiYG hereunto set acid, WHiO consists in causing sulfuric azihymy hand in the PI'GSOIICO of two subscribing 1o drid Ito be abscirbed byl liquiii Sillfillii} acfidi, witnesses;

sup ying simu taneous y Wit 1 t 1e an 1y ri I n a di uting agent in sufficient quantity to keep RUDOLB KN IE1 the liquid acid at its original degree of con- Witnesses:

centration, and coolin the liquid acid Where JACOB ADRIAN,

it absorbs the anhydri JOHN L. HEINKE. 

